1. Field of the Invention
The present invention relates generally to metal extrusion processes and to metal extrusion dies for use therein and, more specifically, to an improved metal extrusion die stack having a direct cone geometry.
2. Description of the Prior Art
In metal extrusion processes, the metal work piece is subjected to heat and pressure, by the application of dies, to form the metal work piece into a desired shape. The appropriate work surfaces of the dies contact the work piece under great pressures such as to force the metal work piece through the die orifice or orifices. Also, the work piece is ordinarily preheated to an appreciable extent to make it more easily deformable under the pressures employed. Thus, in typical extrusion processes, a block or billet of metal at elevated temperature is forced under high pressure to flow through a die having an opening which corresponds to the desired cross-sectional shape of the extrusion to be produced. The metal may be heated in the range of 2300.degree. F., in the case of steel, during the extrusion process.
U.S. Pat. No. 2,738,062, issued Mar. 13, 1956, to Edgecombe, is typical of the prior art extrusion processes in showing an extrusion press in which a front and rear platen are held in accurately spaced relation with one another. Between the platens is mounted a billet container for movement toward and away from the forward platen. The rear platen supports a ram arranged to project into the container and force a billet therein to flow through the die. The die is mounted in a die holder which is releasably engaged in a die carrier aligned with the container passage. The carrier is mounted for movement into and out of the forward platen to move the die into and out of operative relation with the exit or downstream end of the container.
In order to form an extrusion, the container is moved forwardly to seat against the rear face of the forward platen. A die holder and die assembly is meanwhile mounted on the rear face of the carrier and the latter is moved rearwardly into the forward platen to engage the die in a recess in the forward end of the container which is coaxial with the container passage. The carrier is then locked to the forward platen. After a heated billet has been loaded into the container, the ram, carrying a dummy block on its outer end, is moved forwardly under high pressure to force the billet outwardly through the die. The extrusion is then severed and conveyed away from the press.
Even though plain and alloy steels have been extruded successfully for over 40 years, a need exists for an improved steel extrusion apparatus and method which solves many of the difficulties associated with the high temperatures and pressures encountered with steel extrusion processes.
A need exists for such an apparatus and method which includes an improved metal extrusion die stack with removable die inserts which can be easily and more economically changed out in the event of wear.
A need also exists for such a metal extrusion die stack which features an improved die stack geometry of a simple design which saves steps in the prior art extrusion process.
A need also exists for an ultra high strength material which performs well under the extreme temperatures and pressures required in steel extrusion and which reduces die erosion, distortion and fracture.
A need also exists for an improved metal extrusion die stack with a direct cone geometry which facilitates the rapid changing of dies.